The present invention is concerned with plastic fasteners, and more particularly with a plastic fastener having means for latching under a peripheral shoulder of a stud projecting from a surface and comprising a hollow shank within which the stud can be received and with an internal lip or lips to engage the shoulder of the stud.
Plastic fasteners of the foregoing kind for assembly on a T-stud, or studs with annular ribs or a screw thread constituting the peripheral shoulder of the stud, normally have a relatively narrow internal lip around the hollow shanks (or lips round sections of their shanks where the shanks are separated into two or more sections to provide greater resilience and flexibility enabling them to be more readily pushed axially onto studs). The depth of the lips is limited in practice because such fasteners are made by injection molding and, where the shank is closed at its head end, the fastener has had to have the capability of being pulled axially off the internal core of the mold cavity. Such a fastener is described, for example, in United Kingdom Patent Specification No. 1236407.
While fasteners as referred to above are widely used for a variety of purposes, including, for example, securing carpets and mats to the floors of motor vehicles to which suitable studs have been welded, and such fasteners provide adequate retention on the studs for such purposes, there are occasions when it is desired to push a plastic stud axially onto a headed or threaded stud, and obtain a significantly higher resistance to pull-off.
It is accordingly an object of the present invention to provide a plastic fastener for pushing onto a headed or threaded stud which has a higher resistance to pull-off than has been customary hitherto.